In the cutting of pipes it is conventional to mount a cutting torch on the pipe from which a length is to be cut and rotate the torch about the longitudinal axis of the pipe to cut the latter. The pipe may be cut along a plane which is perpendicular to the axis of the pipe, or along a plane which is inclined to the pipe's axis, or along a curvilinear line. Further, the cut edge of the pipe may be either perpendicular to the axis of the pipe or beveled. Typical of apparatus used heretofore in the cutting of pipes are the mechanisms illustrated in Brown U.S. Pat. No. 1,860,653; Brown U.S. Pat. No. 1,885,107; Wheeler U.S. Pat. No. 2,990,169; and Livers U.S. Pat. No. 3,409,282.
When the pipe from which a section is to be cut is out-of round, rather than truly cylindrical, complications are introduced. One of the most common problems encountered when cutting an out-of round pipe is that of maintaining the cutting torch at a uniform distance from the pipe's surface about the entire circumference of the pipe, and particularly if the cut edge of the pipe is being beveled. If the distance from the torch to the pipe surface varies, the resulting line of cut also will vary, thereby precluding the formation of an end surface having the desired configuration.
The difficulties encountered when cutting out-of-round pipes have been recognized heretofore. See, for example, Mighton U.S. Pat. No. 3,265,379 which discloses an attachment for pipe cutting mechanisms of the kind disclosed in the other patents referred to above and which is intended to compensate for out-of-roundness of a straight length of pipe when the latter is being cut at right angles to its longitudinal axis.
In the construction of pipelines it often is necessary to connect a pair of adjacent straight pipe sections by means of a curved tube turn or elbow section. Each end of the tube turn must match the confronting end of the straight section exactly so as to enable a proper weld to be made. Normally, the end of the straight section lies in a plane which is normal to the longitudinal axis of the straight section and, as a consequence, the adjacent end of the confronting tube turn also should lie in the same plane. In the cutting of such tube turn, however, it heretofore has been difficult to form a cut end which is truly normal to the longitudinal axis of the tube turn at the plane of the cut. Unless the plane of the cut end of the tube turn is truly normal to the longitudinal axis of the tube turn at the plane of the cut, however, the resulting configuration of the cut end will be elliptical or some other configuration, rather than cylindrical.
Greene U.S. Pat. No. 3,417,980 discloses apparatus which may facilitate the cutting of tube turns to avoid elliptical ends, provided the tube turn itself is not out-of-round. Unfortunately, however, out-of-round tube turns are commonly encountered. The cutting of an out-of-round tube turn without compensating for the out-of-roundness thus cannot result in a cut end that is truly cylindrical. Heretofore, however, there does not appear to be any provision made for compensating for out-of-roundness of tube turns.